1. Field of the Invention
The present invention relates to high-frequency switching circuits and, in particular, to a high-frequency switching circuit including a high-frequency switch that includes a field-effect transistor (FET) switching element.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 10-93302 discloses a high-frequency switching circuit including a high-frequency switch that includes an FET switching element and that selectively connects between a common input/output terminal and one of a plurality of input/output terminals.
FIG. 1 is a circuit diagram of a high-frequency switching circuit illustrated in Japanese Unexamined Patent Application Publication No. 10-93302. The high-frequency switching circuit 14 includes an antenna terminal ANT arranged to be connected to an antenna, a reception-signal output terminal RX arranged to be connected to a receiving circuit, a transmission-signal input terminal TX arranged to be connected to a transmitting circuit, and a high-frequency switch 12 and is a circuit for switching between a transmission signal and a reception signal.
Matching circuits M1, M2, and M3 are disposed between the antenna terminal ANT and the high-frequency switch 12, between the reception-signal output terminal RX and the high-frequency switch 12, and between the transmission-signal input terminal TX and the high-frequency switch 12, respectively. The matching circuits M1, M2 and M3 perform impedance matching between the respective terminals and the high-frequency switch 12.
The high-frequency switch 12 is made of a semiconductor chip made of, for example, gallium arsenide (GaAs) The chip is bonded to each of the terminals with bonding wire (gold wire). Each of the matching circuits M1, M2 and M3 is designed in consideration of an electric inductance in the bonding wire.
In the matching circuit M1 illustrated in FIG. 1, an inductor LL1 represents an inductance of a lead to the antenna terminal ANT, a capacitor CS1 represents a stray capacitance between the lead of the antenna terminal ANT and the ground, and an inductor Lw1 represents a bonding-wire inductance. A bulk capacitor CM1 is a metal-insulator-metal (MIM) capacitor.
Similarly, the matching circuits M2 and M3 include inductances LL2 and LL3 representing lead components, stray capacitances CS2 and CS3 between the leads of the respective terminals and the ground, bonding-wire inductances LW2 and LW3, and MIM capacitors CM2 and CM3, respectively.
However, to meet a requirement for miniaturization of a high-frequency switching circuit module, it is necessary to reduce the size of a high-frequency switch. In order to reduce the size, flip-chip mounting using bump connection is required.
The inductance of the bump portion in the above flip-chip mounting is significantly less than that in wire bonding. Thus, for the flip-chip mounting, imperfect matching occurs, and an extra line and chip inductor for achieving matching for each terminal is required.